How to load database value to combobox?

Imports System.Data.SqlClient
Imports System.Data
Public Class Form1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim conectionstring As String
        conectionstring = "USER=userid;PASSWORD=password;SERVER=servername;DATABASE=databasename"
        Dim SQLQuery As String = "select  p_id,lastname,firstname from persons123"
        Dim MyConn As New SqlClient.SqlConnection(conectionstring)

        Dim dataset As DataSet = New DataSet()
        Dim dr As SqlDataReader
        MyConn.Open()
        Dim Cmd As New SqlClient.SqlCommand(SQLQuery, MyConn)
        dr = Cmd.ExecuteReader()
        While dr.Read
            ComboBox1.Items.Add(dr(0).ToString())
        End While
    End Sub
End Class